The race between Democrats Hillary Clinton and Bernie Sanders at Monday's Iowa caucuses was so close some precincts had to use a coin flip to determine who would be awarded a county delegate.

Under Iowa's system, more than 11,000 county delegates are divided among the candidates according to voter preferences. The percentage each candidate receives is then converted to their share of about 1,400 state delegates.

Because there are so many more county delegates than state delegates, a candidate's getting one more county delegate does not have a huge effect on the overall outcome.

But Clinton's luck in these situations Monday was remarkable.

Democratic presidential candidate Hillary Clinton, accompanied by her husband, former President Bill Clinton, arrives at her caucus night rally at Drake University in Des Moines, Iowa, Feb. 1, 2016.

In at least six precincts, the support for Sanders and Clinton was close enough that under party rules the final county delegate needed to be decided by a representative trying to guess which side of the coin would land facing up after it was flipped in the air.